[Breaking Change] Version 1.2.0 fixes a bug with ChainCallback() and InsertCallback() methods

[KyryloKuzyk]

Bug Description

Recently a bug was discovered in how Group() works after ChainCallback() or InsertCallback(): https://discussions.unity.com/t/primetween-high-performance-animations-and-sequences/926420/329

The documentation of the Group() method is following:

/// <summary>Groups <paramref name="tween"/> with the 'previous' animation in this Sequence.<br/>
/// The 'previous' animation is the animation used in the preceding Group/Chain/Insert() method call.<br/>
/// Grouped animations start at the same time and run in parallel.</summary>
public Sequence Group(Tween tween) { }

But all PrimeTween versions from 1.1.10 to 1.1.22 had a bug in the way ChainCallback() and InsertCallback() were implemented. When Group() was used after ChainCallback() or InsertCallback(), the grouped animation was inserted at the beginning of the sequence. Instead, the tween should be inserted at the time of callback.

Here is an example:

// for example, this sequence:
Sequence.Create()
    .Group(tween1)
    .ChainCallback(callback)
    .Group(tween2);

// has wrong behavior in PrimeTween [1.1.10 - 1.1.22]: 'tween2' is grouped with 'tween1'
// [tween1]-[callback]
// [tween2]

// the correct behavior: 'tween2' should be grouped with 'callback' (previous operation)
// [tween1]-[callback]
//          [tween2]   

Affected Versions

The bug was introduced in version 1.1.10 and was present in all versions up to 1.1.22.

Breaking Changes

By fixing the bug, version 1.2.0 introduces a breaking change that may affect existing projects. PrimeTween 1.2.0 also comes with an automatic detector that can find potential places where the breaking change may occur. You can also trigger the search for potential issues manually by pressing the 'PrimeTweenInstaller / Find potential issues' button.

If you wish to keep the old incorrect behavior in the existing project, please replace ChainCallback/InsertCallback() calls with ChainCallbackObsolete/InsertCallbackObsolete() calls respectively. There is no need to replace all usages, fixing only methods found by the the detector is enough. If the detector doesn't find any issues, then you don't have to change anything.